MR Simulation

  • Simulator solves the Bloch equation in the rotating frame, by time updated computation of spin magnetization vector at each spatial location in the x-y plane of the selected slice. The Free Induction Decay (FID) signals are acquired in the X and Y receiver coils upon application of a 90 deg. RF pulse in the phase-encode direction. For any pulse sequence, the spin precession frequency in the rotating frame of reference is changed by the application of external spatial encoding gradients. In our current implementation of the simulator, we have been able to simulate the effects of phase and frequency encoding gradients for simple spin-echo and gradient-echo sequences. A 90 deg. hard pulse is assumed to tip the magnetic moments into the transverse plane (x-y). Our discrete-event simulation models the time evolution of the received signals by state changes at a countable number of time points. For each phase encoding step, the MR signal is computed as a summation of each local magnetization vector. .